992K Wheel Loader Caterpillar

Electronic Control Module

Illustration 1	g01309473
ECM connectors and contacts

The "Machine ECM" is located behind the operator seat.

The ECM makes a decision based on input data information and programming parameters that have been flashed to the ECM memory. After the ECM receives the input information, the ECM determines the correct response. The ECM will send an output signal to the appropriate device. The internal input circuits and the internal output circuits of the ECM are connected to the machine wiring harness by two 70 contact connectors (J1 and J2).

Note: The ECM is not serviceable. If the ECM is damaged, the ECM must be replaced. The rate of failure for the ECM is low. If a failure of an ECM is suspected, contact the technical communicator at your dealership for possible consultation with Caterpillar before replacing the ECM. Replace the ECM only after all the other possible causes of a particular problem have been investigated.

Inputs

The machine has several different types of input devices. The ECM receives status information about the machine from the input devices. The ECM then determines the correct output action that is needed to control machine operations. The output action is based on memory and software parameters. The machine utilizes the following types of inputs: switch type and sensor type.

Switches provide signals to the switch inputs of the ECM. The possible outputs of a switch are listed: an open signal, a grounded signal and + battery signal.

Sensors provide an electrical signal to the ECM that constantly changes. The sensor input to the ECM can be one of several different types of electrical signals such as the following: pulse width modulated (PWM) signals, voltage signals, and frequency input signals. Each possible input to each of the "Machine ECM" is listed in the tables for the 70-pin connectors.

Outputs

The ECM sends electrical signals through the outputs. The outputs can create an action or the outputs can provide information to the ECM. The ECM can send output signals to system components in one of the following types of electrical signals: driver outputs, sinking driver outputs, sensor power supply outputs, and data link outputs. The possible outputs for each of the "Machine ECM" are listed in the tables for the 70-pin connectors.

Input/Output

Communication between the "Machine ECM" and between the other ECM modules on the machine are conducted over the data link circuits. The data link circuits allow the sharing of information with other electronic control modules. The data link circuits are bidirectional. The data link circuit allows the ECM to send information and the data link allows the ECM to receive information.

The ECM supports two types of data link systems.

• Cat Data Link

• SAE J1939 (CAN A & B) Data Link

The two types of data links are the main structure for communication between all the control modules on the machine. More than one CAN data link system can be present on a machine. Dedicated CAN data link circuits can be used for communication between specific controls on the machine.

Communication between the "Machine ECM" and between the other control modules on the machine are conducted over the SAE J1939 data link circuit that is connected to each control module. The ECM uses the Cat Data Link to send and to receive information from the Cat Electronic Technician (ET).

A module identifier (MID) is assigned to the "Machine ECM". The MID for the "Machine ECM" is:

Machine ECM - MID 039

Note: The following tables list the circuit connections for the "Machine ECM".

Input Components

Illustration 2	g02731068
Implement ECM input components (1) Implement ECM (2) Bucket Raise Kickout Switch (3) Bucket Tilt Kickout Switch (4) Bucket Lower Kickout Switch (5) Keypad (6) CAN B Data Link (7) Lift Lever Position Sensor (8) Tilt Lever Position Sensor (9) Lift Linkage Position Sensor (10) Tilt Linkage Position Sensor (11) Implement Lockout Switch (12) Implement Pilot Pressure Sensor (13) Hydraulic Oil Temperature Sensor (14) Implement Tank Oil Level Sensor (LOW) (15) Implement Tank Oil Level Sensor (FULL) (16) Lift Cylinder Head End Pressure Sensor (17) Lift Cylinder Rod End Pressure Sensor (18) Right Implement Pump Pressure Sensor (19) Left Implement Pump Pressure Sensor (20) PCS Store Switch (21) Implement Pump Case Drain Oil Filter Bypass Switch (22) Implement Pilot Oil Filter Bypass Switch (23) HVAC Auto/Manual Switch (24) HVAC Pressure Switch (25) HVAC Cab Temperature Sensor (26) HVAC Evap Thermostat Temperature Sensor (27) HVAC Temperature Switch (28) HVAC Louver Temperature Sensor (29) Steering Case Drain Oil Filter Bypass Switch (30) Steering Tank Oil Level Sensor (LOW) (31) Steering Tank Oil Level Sensor (FULL) (32) Steering Pilot Oil Filter Bypass Switch (33) Primary Steering Pressure Switch (34) Steering Oil Temperature Sensor (35) Steering Pilot Oil Pressure Sensor (36) Fan Return Oil Filter Bypass Switch (37) Fan Pressure Sensor (38) Fan Case Drain Filter Bypass Switch (39) Wiper Fluid Add Switch

Sensors

Sensors provide signals to the ECM about changing conditions. The signals change in a proportional manner to reflect the changing conditions. The types of signals that are recognized by the ECM are listed below:

Frequency (Hz) - The sensor produces a signal that varies the frequency as the condition changes.

Pulse width modulation (PWM) - The sensor produces a signal that varies the duty cycle as the condition changes. The frequency of this signal is constant.

Temperature Sensors

Temperature sensors include:

• Hydraulic Oil Temperature Sensor

• Steering Oil Temperature Sensor

• Cab Air and Cab Ventilation Duct Temperature Sensor

• Evaporator Coil Temperature Sensor

Illustration 3	g06124270
Hydraulic/Steering Oil Temperature Sensor

Note: The machine is equipped with steering and hydraulic oil temperature sensors.

The temperature sensor for the hydraulic oil informs the ECM of the temperature of the hydraulic system oil.

The sensor sends an analog signal to the Implement ECM indicating hydraulic oil temperature. The resistance range for this sensor is 33,650 ohms at −40° C (−40° F) to 18.6 ohms at 150° C (302° F).

Illustration 4	g06124247

The steering oil temperature sensor allows the implement ECM to monitor the temperature of the transmission oil. The temperature sensor outputs a pulse width modulated signal. The duty cycle of the signal will vary in proportion to the temperature. These PWM signals are inputs to the ECM.

Illustration 5	g06124270

Cab Air and Cab Ventilation Duct Air Temperature Sensors are passive analog inputs to the implement ECM. These two sensors are used to determine average cab air temperature.

Illustration 6	g06125611

The HVAC evaporator thermostat switch is a passive analog signal to the Machine ECM. This sensor is used to measure the temperature of the evaporator coil.

Illustration 7	g06125819

The climate control system automatically adjusts the heating and air conditioning to maintain a consistent cab temperature.

Illustration 8	g06125833

Blower driver module is used to control the blower speed on an HVAC blower motor. The driver controls the blower speed by varying the current going to blower motor. The controller will vary the current from 99% down to 35% of full rated speed.

Level Sensors

Level Sensors include:

• Implement Tank Oil Level High Sensor

• Implement Tank Oil Level Low Sensor

• Steering Tank Oil Level High Sensor

• Steering Tank Oil Level Low Sensor

Illustration 9	g06124318

There are two hydraulic oil level sensors (Low and High) that monitor the implement hydraulic tank oil level.

Illustration 10	g06124318

There are two hydraulic oil level sensors (Low and High) that monitor the steering hydraulic tank oil level.

Pressure Sensors

Pressure sensors include:

• Implement Pilot Pressure Sensor

• Steering Pilot Pressure Sensor

• Fan Pressure Sensor

• Right and left Implement Valve Pressure Sensors

• Lift Cylinder Rod End pressure sensor

• Lift Cylinder Head End pressure sensor

Illustration 11	g06124543

The pressure sensor sends a signal to the Implement ECM indicating system pressure. The pressure sensor outputs a pulse width modulated signal. The duty cycle of the signal will vary in proportion to the system pressure. These PWM signals are inputs to the ECM.

Illustration 12	g06124543

The pressure sensor sends a signal to the Implement ECM indicating system pressure. The pressure sensor outputs a pulse width modulated signal. The duty cycle of the signal will vary in proportion to the system pressure. These PWM signals are inputs to the ECM.

Illustration 13	g06124543

The pressure sensors send a signal to the Implement ECM indicating the lift cylinder rod end and head end pressures. When an implement is activated, oil from the implement control valve is directed to the lift cylinders and/or tilt cylinder.

Position Sensors

Position sensors include:

• Lift lever position sensor

• Tilt lever position sensor

• Lift linkage position sensor

• Tilt linkage position sensor

Illustration 14	g06124636
Typical lift/tilt control

The lift/tilt lever position sensors signal the Implement ECM the position of the lift/tilt control levers. The position sensors are located in the base of the lever.

Illustration 15	g06124752
Prophet handle (option)

The lift/tilt lever position sensors signal the Implement ECM the position of the lift/tilt control levers. The position sensors are located in the base of the handle.

Illustration 16	g06124830

The lift linkage position sensor is bolted to the right side of the front frame near the A pin. The lift linkage position sensor constantly monitors the position of the lift linkage and sends the lift linkage position information to the Implement ECM.

The tilt linkage position sensor is bolted to the right side of the lift arm near the tilt linkage pin. The tilt linkage position sensor constantly monitors the position of the tilt linkage and sends the tilt linkage position information to the Implement ECM.

When the operator moves the lift lever or the tilt lever, the Implement ECM analyzes the signal from the respective lever position sensor, the signal from the lift linkage position sensor, and the signal from the tilt linkage position sensor. The Implement ECM then sends a proportional signal to the respective control valve solenoid.

Inclination Level Sensor (Optional)

Illustration 17	g06125382

Inclination Level Sensor is used in scaleless calibration and is CAN operated. The inclination sensor can be configured for either single axis or dual axis operation.

Switches

Switches provide one of the following types of inputs to the ECM:

• Open

• Ground

• +Battery

Switches are devices that have two states, opened or closed.

• When a switch is open, no signal is provided to the corresponding input of the ECM. This condition is also referred to as floating.

• When a switch is closed, a ground signal or a +battery signal is provided to the ECM.

Cab Air Temperature AUTO / ON switch

Illustration 18	g06125298

The air conditioning auto / on switch has three positions:

• A/C mode: When, the A/C Auto Switch is in the Top position the air conditioning compressor is engaged.

• Center Off When the A/C auto switch is in the Off positions, the temperature select dial is used to control the position of the water valve actuator. When the temperature dial is fully rotated in the counter clockwise position, the water valve will be closed. The water valve will be fully open when the temperature dial is in the full clockwise position. Instead of the temperature dial controlling the water valve directly, the voltage signal from the temperature dial potentiometer will first travel through an ECM, which will then control the valve with the PWM signal.

• Auto Mode:When the A/C Auto switch is in the Bottom position. The temperature dial will be used to communicate the cab temperature requested by the operator to the ECM. In automatic climate control, the implement ECM monitors the cab air recirculation temperature sensor and the HVAC housing air duct outlet sensor. Based on the temperature difference, the ECM energizes or de-energizes the A/C clutch on the compressor clutch coil and adjusts the water valve spool position to maintain a constant louver outlet temperature based on the dial setting.

Kickout Switches

Illustration 19	g06125074
(7) Raise Kickout Button (8) Lower Kickout Button (9) Tilt Kickout Button

The kickout buttons are now on the new keypad, which is located on the right side panel in the cab.

The raise kickout button (7), the lower kickout button (8), and the tilt kickout (9) button all operate the same. When setting a kickout position, operate the appropriate implement control lever to set the lift arms or bucket to the desired kickout position and then return the control lever to the HOLD position.

When a kickout button is pressed, a signal is sent over the CAN B Data Link to the Implement ECM via the Power Train ECM. The Implement ECM stores the current lift or tilt cylinder position, flashes the center LED on the switch panel twice, then illuminates the center LED and sounds an alarm indicating that the kickout position is set.

The kickout position can be disabled with Advisor or Cat ^® Electronic Technician (ET). When disabled, the Implement ECM turns off the center LED.

Implement Lockout Switch

Illustration 20	g06125267
Implement (Hydraulic) Lockout Switch

The Implement ECM will control the operation of the Implement Pilot Supply Solenoid according to the position of the Hydraulic Lockout Switch. Certain fault conditions will also cause the Implement ECM to use the solenoid valve to disable hydraulic operation.

The ECM will disable the operation of the Implement System when the switch is in the LOCK position.

When the switch is in the UNLOCK position, the normally closed switch contacts will ground the input circuit at ECM contact J1-34. When the ECM detects this grounded circuit, the ECM will energize the Implement Pilot Supply Solenoid. The energized solenoid will allow pilot oil to be supplied to the implement control valve.

When the switch is in the LOCK position, the normally open switch contacts will ground the input circuit at ECM contact J1-33. When the ECM detects this grounded circuit, the ECM will de-energize the ON/OFF output for the Implement Pilot Supply Solenoid. Pilot oil will be blocked from the implement control valve.

CPM (Caterpillar Production Measurement) Store Switch

Illustration 21	g06125327

The CPM Store Switch is installed on the machine when the Caterpillar Production Measurement attachment is installed.

When the Production Measurement feature is active, the CPM Store Switch is used to store the current truck information in the Implement ECM memory. The switch is also used to reset the current truck weight and machine bucket weight to zero.

When the CPM Store Switch is pressed, the ECM will detect that the switch input circuit is grounded. The Implement ECM response will be dependent on the CPM mode that is currently active.

Primary Steering Pressure Switch

Illustration 22	g02731847

The primary steering pressure switch is a pressure switch that is used to determine if there is sufficient pressure in the primary steering system. This switch has two outputs, one that is normally open and one that is normally closed. When the pressure in the primary steering system drops below the threshold, the outputs become closed and open respectively.

Fan Return Filter / Steering Oil Filter Bypass Switch

Illustration 23	g02731808

The filter bypass switch alerts the Implement ECM when oil is bypassing the filter.

Implement Pilot Oil Filter Bypass Switch

Illustration 24	g06126216
Implement Pilot Oil Filter Bypass Switch

Illustration 24 shows the implement pilot oil filter below an access panel behind the cab. Supply oil from the fan pump flows through the pilot oil filter to the pilot pressure reducing valve (not visible).

The oil filter bypass switch alerts the Implement ECM when oil is bypassing the filter.

Implement Pump / Fan Pump / Steering Pump Case Drain Oil Filter Bypass Switch

Illustration 25	g02731808

The implement pumps case drain filter and the fan pump/fan motor case drain filter are on the right side of the rear frame by the implement pumps. The case drain filters remove contaminants from the case drain oil before the oil enters the implement hydraulic tank.

The case drain oil filters each contain a bypass switch that alerts the Implement ECM if a filter is restricted.

Window Wiper Fluid Add Switch

Illustration 26	g06126365

A/C Pressure LOW Switch

Illustration 27	g06125890

The Low-pressure switch is used to monitor the refrigerant pressure that comes into the suction side of the refrigerant compressor. The pressure switch prevents the compressor from operating when the pressure for the suction line fails to maintain a specific pressure range. This switch is electrically connected in series with the compressor protection time delay relay, the high low-pressure switch, and the thermostat for the evaporator coil. The compressor will not operate when the Low-pressure switch is OPEN. When the Low-pressure switch is CLOSED, a ground signal is sent to the compressor protection time delay relay. A CLOSED low-pressure switch indicates that the pressure for the suction line is high enough to allow the refrigerant compressor to operate. The compressor protection time delay relay will then turn on causing the compressor to operate.

The switch contacts on the low-pressure switch will move OPEN whenever the pressure value for the suction line decreases to less than 34.5 kPa (5 psi). The switch contacts will remain in the OPEN position until the pressure value increases to 103 kPa (15 psi)or more

A/C Pressure HIGH Switch

Illustration 28	g06125936

The High-Low pressure switch is used to monitor the refrigerant pressure that is coming out of the discharge side of the refrigerant compressor. The pressure switch prevents the compressor from operating when the pressure in the discharge line exceeds a specific pressure range or when the pressure in the discharge line fails to maintain a specific pressure range. This switch is electrically connected in series with the magnetic clutch for the refrigerant compressor, and the evaporator coil thermostat. Similarly to the thermostat switch, the compressor will not operate when the High-Low pressure switch is OPEN. When the High-Low pressure switch is CLOSED, the current moves through the switch and through the coil assembly in the magnetic clutch. This causes the compressor to operate.

The High-Low pressure switch has two pressure set points that will cause the switch contacts to OPEN. For a low-pressure condition, the switch contacts will move OPEN whenever the pressure value for the discharge line decreases to less than 172 kPa (25 psi). The switch contacts will remain in the OPEN position until the pressure value increases to 276 kPa (40 psi) or more. For the high-pressure condition, the switch contacts will move OPEN whenever the pressure value for the discharge line exceeds 2792 kPa (405 psi). The switch contacts will remain in the OPEN position until the pressure value decreases to 1758 kPa (255 psi) or less.

Output Components

Illustration 29	g02731078
(1) Implement ECM (2) Pilot On/Off Solenoid (3) Two Tilt Back Solenoids (4) Two Dump Solenoids (5) Two Lift Lower Solenoids (6) Two Lift Raise Solenoids (7) Left Pump Solenoid (8) Right Pump Solenoid (9) Tilt Regeneration Solenoid (10) Tilt Dual Relief Solenoid (11) Left Float Solenoid (12) Right Float Solenoid (13) Forward Horn Relay (14) HVAC Clutch Coil

The Implement ECM determines outputs based on information that is input to the ECM and information in memory. The Implement ECM then sends a corresponding response through the outputs. The inputs and outputs are connected to the Implement ECM through the machine harness and contact connectors J1 and J2.

Solenoids

All of the solenoids are outputs of the Implement ECM. Each solenoid has a connector with two contacts. The ECM will apply electrical current to the appropriate solenoid when the operator moves the Implement Levers. The ECM uses the solenoid valves to directly modulate the oil pressure to the implements. The ECM uses a PWM signal in order to vary the current to the solenoid. The solenoid current determines the amount of oil pressure that is applied to the implements. The travel distance of the solenoid plunger is proportional to the amount of current that is being sent to the solenoid. An increase in electrical current further opens the solenoid valve.

Pilot / Implement Solenoids

Illustration 30	g06126981
Implement Control Valve (1) Tilt Back (Rack) Solenoids (2) Lift Lower Solenoids (3) Dump Solenoids (4) Lift Raise Solenoids (5) Pilot On/Off Solenoid

The Pilot On/Off Solenoid (5) is located in the front of the Main Control Valve.

This solenoid controls the pilot valve, which enables or disables the pilot hydraulic system. When the Pilot On/Off Solenoid is energized, pilot oil flows to the Pilot Hydraulic Actuators. When de-energized, pilot oil is blocked at the solenoid valve.

The Implement Control Valve is located in the front frame (NEEF) below the lift arms.

The pilot hydraulic actuator solenoids control the movement of the valves for each circuit. When the operator moves a control lever, the control lever sensor sends a pulse width modulated (PWM) signal to the Implement ECM. The Implement ECM analyzes the signals from the control lever sensor, the lift linkage position sensor, and the tilt linkage position sensor. The Implement ECM then sends a proportional current to ENERGIZE the respective pilot hydraulic actuator solenoid.

• The Tilt Back Solenoids (1), also known as Rack Back Solenoids, control the tilt actuators. The tilt actuators direct pilot oil from the tilt end of the main control valve spool to the tank.

• The Lift Lower Solenoids (2) control the lift lower actuators. The lift lower actuators direct pilot oil from the lift lower end of the main control valve spool to the tank.

• The Dump Solenoids (3) control the dump actuators. The dump actuators direct pilot oil from the dump end of the main control valve spool to the tank.

• The Lift Raise Solenoids (4) control the lift raise actuators. The lift lower actuators direct pilot oil from the lift lower end of the main control valve spool to the tank.

Implement Pump Solenoids

Illustration 31	g06126999
(1) Implement Pump Solenoid (2) Implement Pump

The Implement Pump Solenoids control the Implement Pump swashplate angles. The solenoids receive current from the Implement ECM to control oil flow to the pump actuators to control the pump output oil flow.

Tilt Regeneration Solenoid

Illustration 32	g06127195
(1) Tilt Regeneration Solenoid (2) Tilt Regeneration Valve

The Tilt Regeneration Solenoid (1) is located on top of the tilt cylinder. The Tilt Regeneration Solenoid controls the Tilt Cylinder Regeneration function by draining the pilot oil from the Tilt Regeneration Valve (2).

Dual Tilt Relief Solenoid

Illustration 33	g02732052
(1) Dual Tilt Relief Solenoid (2) Pressure tap (3) Dual Tilt Relief Valve

The Dual Tilt Relief Solenoid (1) is located on the right side of the front frame (NEEF). The solenoid controls the Dual Tilt Relief function by directing pilot oil to the Dual Tilt Relief Valve (3). The Dual Tilt Pilot Pressure can be checked at the pressure tap (2) on the Dual Tilt Valve manifold.

Float Valve Solenoids

Illustration 34	g02732073
(1) Left Float Valve Solenoid (2) Right Float Valve Solenoid (3) Left Float Valve (4) Right Float Valve

The Left Float Valve Solenoid (1) and the Right Float Valve Solenoid (2) are located on the right side of the front frame. When the FLOAT function is activated, the Implement ECM energizes the Float Solenoids, which direct the Lift Cylinder head end oil to the tank.

The Float Solenoids are also used during engine starting. The Float Solenoids are energized while the engine is cranking to reduce the load on the engine. Once the engine has reached low idle, the solenoids are de-energized.

Forward Horn Relay

Illustration 35	g06127331

Relays are output tools of the ECM. They allow the ECM to control components that require battery voltage to function to be activated by a low voltage signal. When an input is received, the ECM commands a signal voltage to the relay in the component circuit. The energized relay magnetically switches the battery supply voltage circuit closed and supplies the component with battery voltage.

Illustration 36	g06127361

The Forward Horn Relay is energized to power the Forward Horn. The signal to the relay comes from Implement ECM connector contact J2-2.

HVAC Compressor Clutch Coil

Illustration 37	g06127346
(1) HVAC Compressor (2) HVAC Compressor Clutch Coil (and Pulley Assembly)

The Implement ECM controls the HVAC Compressor Clutch (2) on and off cycles. Implement ECM output is at connector contact J2-3.